Horton

Re: Shouldn't jsonpath .string() Unwrap?

David G. Johnston <david.g.johnston@gmail.com>

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From: "David G. Johnston" <david.g.johnston@gmail.com>
To: "David E. Wheeler" <david@justatheory.com>, andrew@dunslane.net
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-06-12T20:02:44Z
Lists: pgsql-hackers

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  1. Teach jsonpath string() to unwrap in lax mode

On Sat, Jun 8, 2024 at 3:50 PM David E. Wheeler <david@justatheory.com>
wrote:

> Hackers,
>
> Most of the jsonpath methods auto-unwrap in lax mode:
>
> david=# select jsonb_path_query('[-2,5]', '$.abs()');
>  jsonb_path_query
> ------------------
>  2
>  5
> (2 rows)
>
> The obvious exceptions are size() and type(), which apply directly to
> arrays, so no need to unwrap:
>
> david=# select jsonb_path_query('[-2,5]', '$.size()');
>  jsonb_path_query
> ------------------
>  2
> (1 row)
>
> david=# select jsonb_path_query('[-2,5]', '$.type()');
>  jsonb_path_query
> ------------------
>  "array"
>
> But what about string()? Is there some reason it doesn’t unwrap?
>
> david=# select jsonb_path_query('[-2,5]', '$.string()');
> ERROR:  jsonpath item method .string() can only be applied to a bool,
> string, numeric, or datetime value
>
> What I expect:
>
> david=# select jsonb_path_query('[-2,5]', '$.string()');
>  jsonb_path_query
> —————————
>  "2"
>  "5"
> (2 rows)
>
> However, I do see a test[1] for this behavior, so maybe there’s a reason
> for it?
>
>
Adding Andrew.

I'm willing to call this an open item against this feature as I don't see
any documentation explaining that string() behaves differently than the
others.

David J.